It is a continuing goal of firearm manufacturers to increase the performance level of their products. It is often a goal to increase the velocity of the bullet exiting the firearm.
A typical firearm includes a barrel, a receiver, and a breech block or bolt. The barrel is generally a tubular member out of which the bullet exits after firing. The receiver of the weapon is connected to the barrel and the ammunition is placed into an opening or chamber in the receiver prior to firing. The ammunition may be placed in the chamber either manually or automatically, with the use of a magazine. The ammunition is placed in the chamber of the receiver so that the bullet faces the entrance to the barrel. The rear end of the ammunition, which generally houses gun powder, faces the bolt or breech block. The bolt or breech block typically houses the firing pin which is used to ignite the primer in the ammunition. The primer then ignites the gun powder. The bolt or breech block is also used to close off the rear end of the ammunition so that when the ammunition is fired, the bullet goes out the barrel, not through the rear end of the firearm.
There are two types of ammunition which are commonly used, caseless cartridges and cartridges with cases. With both types of ammunition, the gun powder is usually ignited by a primer which is located on an outside surface of the ammunition. With rim-fired ammunition, the primer charge is located around the rim, or external edge, of the ammunition. With center-fire ammunition, the primer is located in the rear of the ammunition in the vicinity of the bolt.
With caseless ammunition, the projectile exits through the barrel of the gun so that after the ammunition is fired, nothing remains in the chamber of the receiver. With cartridges with cases, the projectile or bullet exits through the barrel and the empty casing remains in the receiver. In both cases, there is a need to extract the remaining ammunition from the receiver in order to fire another round of ammunition. With caseless ammunition, there is a possibility that the ammunition in the receiver chamber will misfire and will require manual removal. With cartridge cases, the empty casing must be removed before the next cartridge can enter the receiver chamber. Therefore, it is known to provide means for extracting both caseless ammunition which has misfired and empty casings from the chamber of the receiver of the weapon. With automatic or semi-automatic weapons, the extractor works in combination with an ejector to automatically eject the casing from the chamber. An ejector arm in the receiver strikes the case from the side, ejecting it out a port in the receiver.
There are several ways to extract casings and misfired ammunition from the chamber of the receiver. The first involves the use of external extractors and the second involves the use of internal extractors.
With external extractors, the cartridge casing or caseless cartridge typically includes a rim or exterior groove on the cartridge for gripping by an extractor. The rim or groove may also be used for positioning and maintaining the cartridge in the chamber. For proper extractor functioning, the rim or groove must be accessible from the face of the bolt to enable the extractor to grip the rim or groove. When the extractor is positioned behind the rim or within the groove on the cartridge and the bolt is moved rearward within the receiver of the gun, the cartridge may be removed from the chamber either manually or automatically.
One problem which is associated with cartridges used with external extractors is that the rim or groove may cause a weakened or defective cartridge to fracture along the rim or groove during firing. When the cartridge fractures during firing, the cartridge explodes or blows back into the weapon receiver. This may result in damage to the weapon and injury to the user. The likelihood of blow-back is more common with reloaded ammunition where firings have weakened the cartridge. In order to avoid damage to the weapon and the user from blowback, conventional weapons with external extraction have bolt ends which have a diameter greater than the cartridge case head at the rear of the cartridge so that the extractor can grab the external rim for extraction. Receivers for conventional weapons must be sized to accommodate these bolt ends, which results in heavy bolts with proportionally larger receivers. The combination results in a heavy weapon. Cartridge diameter along with bullet weight has, therefore, been an important factor in the design of firearms, which for lighter weapons means smaller diameter cartridges.
In conflict with the desire to keep weight down has been the desire to increase bullet velocity. A shorter, wider cartridge case is more efficient than a longer, narrower cartridge case of the same powder capacity. A shorter, wider cartridge case has a larger powder surface area to burn. A longer, narrower cartridge case, at the moment of ignition, requires greater energy to push the unburned powder weight along with the bullet weight through the throat of the barrel. A shorter, wider case reduces the height of the column of powder that is pushed with the bullet. The result, with the shorter wider casing, is more efficient energy utilization and higher bullet velocity from the same weight of powder.
A greater powder burn area and a shorter powder column also provides for a faster, more complete burn, driving a greater burn efficiency that also translates to an increase in gas production and a greater bullet velocity. In earlier cartridges, greater powder charges have been used to produce higher bullet velocities, but this creates a pressure condition in the cartridge case which can result in blowback.
Therefore, it is desirable to provide a weapon with a shorter, wider cartridge case, but without increasing the size and weight of the weapon.
U.S. Pat. No. 29,836 to Maxim, U.S. Pat. No. 4,676,017 to Hurlemann et al., and U.S. Pat. No. 5,024,016 to Smith describe external extractors. U.S. Pat. Nos. 125,830 to Milbank, 674,751 to Bailey, 2,083,665 to Pihl et al., 2,573,451 to Keller et al., and 4,149,465 to Verkozen describe ammunition cartridges which incorporate an external rim or groove for external extraction.
With internal extractors, the cartridge casing or caseless cartridge typically includes a rim or groove on the interior of the end of the cartridge for gripping by an internal extractor. With internal extractors, the end of the extractor and bolt end may be inserted into a cavity inside the cartridge so that the bolt end fits closely in the cavity of the cartridge. This may reduce the likelihood of blowback.
U.S. Pat. No. 1,713,954 to Destree describes an internal extractor for use with a cartridge having an inwardly extending flange at the bolt end. The extractor in this invention is part of the firing pin so that the extractor/firing pin strikes the primer in a cavity of the cartridge. The extractor/firing pin is biased upwardly and the extractor end of the firing pin has an angled edge. When the extractor/firing pin is being inserted into the cartridge, a sloped surface on an upper edge of the extractor/firing pin engages the flange on the cartridge against the upward force of a spring which allows the extractor/firing pin to enter the cavity of the cartridge. Once the extractor/firing pin has passed by the flange, the spring forces the extractor/firing pin upward to engage the cavity behind the flange so that the casing may be removed from the chamber after firing.
U.S. Pat. No. 3,680,242 to Wiese describes an internal extractor which is pivoted upward to engage a flange formed on the rear end of the projectile when the firing pin moves forward to fire the charge.
U.S. Pat. No. 4,395,838 to Civolani describes an ejector for use with caseless cartridges in conjunction with a cartridge design. The ejector engages an interior surface of the cartridge to hold the cartridge in position when the cartridge has not fired but allows the cartridge to exit the barrel when the charge in the cartridge is fired.
U.S. Pat. No. 4,895,064 to Marzocco describes an internal extractor in combination with a cartridge where the extractor extends from the face of the bolt to engage an inner chamber of a caseless cartridge.
U.S. Pat. No. 3,618,246 to Woodring discloses a caseless cartridge having an inwardly extending flange at one end of the cartridge for engaging an extractor.
Among other things, it is desirable to provide an improved extractor system wherein the end of the bolt and the extractor effectively enter the cavity of the cartridge. It is, likewise, preferred to provide a cartridge which is the same diameter as the bolt. It is also desirable to provide an extractor which exerts a positive rotational force on the cartridge to more reliably remove the cartridge from the chamber. In addition, it is desirable to provide a method for manufacturing a cartridge for use with internal extraction. Further, it is desirable to provide a reinforced receiver for mating with the barrel which reduces the amount of machining necessary to provide a precision fit between the barrel and receiver and to further reinforce the chamber of the firearm.